This invention relates generally to the field of turbochargers and, more particularly, to a turbocharger annular seal gland seal that is designed having a reduced or eliminated centrifugal stress during use, thereby providing improved turbocharger operating life.
Turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting the intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Specifically, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine to spin within the housing. The exhaust gas-driven turbine is mounted onto one end of a shaft that is common to a radial air compressor mounted onto an opposite end of the shaft. Thus, rotary action of the turbine also causes the air compressor to spin within a compressor housing of the turbocharger. The spinning action of the air compressor causes intake air to enter the compressor housing and be pressurized or boosted a desired amount before it is mixed with fuel and combusted within the engine combustion chamber.
The common shaft extending between the turbine and compressor is disposed through a turbocharger center housing that includes a bearing assembly for: (1) facilitating shaft rotating action; (2) controlling axially directed shaft thrust effects and radially directed shaft vibrations; (3) providing necessary lubrication to the rotating shaft to minimize friction effects and related wear; and (4) providing a seal between the lubricated assembly and the turbine and compressor housings. The common shaft as used in turbocharger applications is known to have shaft-rotating speeds on the order of 60,000 to 80,000 rpm or higher. Under such operating conditions it is imperative that the bearing assembly provide sufficient lubrication to the shaft to minimize the extreme friction effects that take place at such high rotating speeds, thereby extending shaft service life.
An annular seal gland is installed in the turbocharger center housing and is used to both control axially directed thrust imposed on the shaft from the turbine housing shaft end, i.e., act as a thrust bearing, and to provide a leak-tight seal between the gland and the housing. Because the annular seal gland is interposed between the rotating shaft and static housing surfaces, it is exposed to centrifugal forces that are known to impose a hoop stress onto conventionally designed glands. Such hoop stresses are known to cause the gland to experience fatigue failures. This type of failure adversely impacts the gland""s ability: (1) to handle thrust loads; (2) effectively provide friction and heat reducing lubricant to the shaft; and (3) to provide a leak-tight seal between the gland and the housing. An adverse impact on any of these gland performance functions is known to ultimately reduce the service life of the turbocharger.
It is, therefore, desired that a turbocharger annular seal gland be constructed in such a manner as to reduce or eliminate altogether the high centrifugal hoop stresses that can be imposed thereon by placement of the gland between the rotating shaft and static housing. It is also desired that the annular seal gland so constructed be capable of reducing these stresses without adversely impacting the lubricating, thrust load handling, and sealing functions of the gland. It is further desired that the annular seal gland so constructed be capable of retrofit to existing turbocharger devices without extensive redesigning.
Turbocharger annular seal glands, constructed according to principles of this invention include: (1) a thrust bearing section adjacent a first gland end; (2) a seal groove around an outside gland surface at a gland end opposite the thrust bearing section; and (3) a plurality of open faced lubricant pumping grooves disposed radially along an axial gland surface that mates against an adjacent turbocharger center housing surface. Configured in this manner, annular seal glands of this invention reduce or eliminate the formation of circumferential hoop stresses that can cause fatigue failure and ultimately reduce turbocharger service life.